Hypervelocity jet and projectile velocity augmenter



P 9, 1969 w. c. COOLEY 3,465,639

HYPERVELOCITY JET AND PROJECTILE VELOCITY AUGMENTER Original Filed July 22, 1966 3 Sheets-Sheet 1 FIG. 1.

INVENIOR WlLLlAM C. COOLEY W. C. OLEY S pt. 9 69 HYPERVELOCI'IY JET AND PROJEC'IILE VELOCITY AUGMENTER Original Filed July 22. 1966 5 sh86t heet 2 INVENTOR WILLIAM C. CQ LEY A NEY Sept. 9, 1969 w. c. COOLEY HYPERVELOCITY JET AND PROJECTILE VELOCITY AUGMENTER Original Filed July 22, 1966 5 Sheets-Sheet 5 United States Patent H 3,465,639 HYPERVELOCITY JET AND PROJECTILE VELOCITY AUGMENTER William C. Cooley, Bethesda, Md., assignor to Exotech Incorporated, Rockville, Md. Continuation of application Ser. No. 568,368, July 22, 1966. This application Dec. 5, 1967, Ser. No. 688,266

Int. Cl. F41f 1/00 US. Cl. 898 12 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation of application Ser. No. 568,368, filed July 22, 1966, now abandoned, which is a continuation-in-part of application Ser. No. 355,115, filed Mar. 26, 1964, now abandoned, of the same inventor.

This invention relates to apparatus and a method for producing high velocity fluid jets of material by an impact process and t0 apparatus and a method for augmenting the velocity of gun-launched projectiles by immersion in such a high velocity jet.

The principle of shaped charges has undergone investigation for many years, but has always been con cerned with the use of detonating explosive materials. The basic principle of jet formation by the collision of fluid or solid surfaces at an angle, however, is much more general, and can be given the name cumulation or the cumulative effect. Cumulation may be defined generally as the concentration of energy into a small volume of fluid by the interaction between two material surfaces, at least one of which behaves as a fluid, when the surfaces collide at an angle. A simple example is the formation under a boat bow of a water jet moving ahead faster than the boat when its hull bottom planes at a small angle above the water surface. This phenomenon is caused by the hydrodynamic motion which produces a stagnation point on the hull a short distance back from the forward water line. Water streamlines above the stagnation streamline are forced to turn upward and reverse direction, conserving their kinetic energy relative to the moving stagnation point, and escaping forward with a velocity of as much as twice the boat velocity.

The main object of this invention is to provide apparatus which can produce this cumulative eifect by converging collision of materials in an axi-symmetric geometry to for-m a pulsed axi-symmetric jet of liquid, gas or plasma which utilizes the kinetic energy of a sabot or piston in an impact process.

Another object of the invention is to provide a velocity augmenter adapter for use with a powder gun, gas gun, or other projectile accelerator which can accelerate the projectile to hypervelocity without shattering or excessively ablating the projectile.

Another object is to provide a device for accelerating projectiles to hypervelocity using simple construction and compact design which can be applied to an anti-missile or anti-aircraft Warhead to be used to launch a projectile at a target, or to be used in an anti-tank mine capable of launching a projectile from underground, or to be used for penetrating a pill box or other fortification by firing a projectile through a thick wall.

Further, the present invention can be used with an antiaircraft or anti-missile gun, capable of sending a projectile to high altitude and with a straighter trajectory and shorter elapsed time to reach the target than previously possible.

Further, the present invention can be used to launch simulated meteoroids to velocities in the range above 20,000 feet per second to permit research on meteoroid impact phenomena.

Further, the present invention can be used to launch projectiles of known mass and geometry to hypervelocity to permit controlled terminal ballistics research on impact phenomena at velocities which can presently only be achieved with chemical explosive or electrically actuated launchers which generally damage the projectile.

Further, the present invention can be used without a solid projectile to provide a pulsed jet of high stagnation pressure for research, military or industrial purposes, in particular, a repetitive firing Water cannon for use in rock-breaking, tunneling, mining and other uses.

In accomplishing the aforesaid velocity augmentation objects, the present invention utilizes a velocity augmenter comprising one or more stages of augmentation wherein the employed combination of simple equipment includes a propelling means, a driver sabot carrying a detachable projectile, a tubular booster unit, and a casing to hold the components in proper geometrical relationship and to resist the high internal pressures generated during operation.

Other objects and many of the attendant advantages of the present invention will become apparent as the same becomes better understood from the following detailed description had in conjunction with the annexed drawings, wherein:

FIG. 1 is a longitudinal sectional view of one embodiment of the velocity augmenter for projectiles in the present invention;

FIG. 2 is a longitudinal sectional view of a further embodiment of the velocity augmenter depicting a converging-diverging nozzle structure in the casing;

FIG. 3 is a longitudinal section of yet another embodiment of the velocity augmenter with a diverging nozzle structure incorporated in the booster unit;

FIG. 4 is a longitudinal section of yet another embodiment of the velocity augmenter utilizing multiple stages;

FIG. 5 is a longitudinal sectional view of yet another embodiment of a velocity augmenter in which a variable diameter booster unit is used and a hollow cylindrical sabot is shown as a generally applicable alternate design;

FIG. 6 is a longitudinal sectional view of a chemical explosive projectile launcher and velocity augmenter;

FIG. 7 is a longitudinal section of a hypervelocity jet and velocity augmenter employing a liquid booster material;

FIG. 8 is a cross-sectional view taken along line 88 of FIG. 7;

FIG. 9 is a longitudinal sectional view of the embodiment shown in FIG. 7; and

FIG. 10 is a cross-sectional view of the device shown in FIG. 9 taken along the line 10-10.

Referring now to the drawings, and more particularly to FIG. 1 wherein one form of the present invention is illustrated, 1 designates a'casing having a hollow cylindrical shape defining a bore 2. The casing is shown to be mounted on the muzzle 6 of a gun or alternate tubular launcher for accelerating a sabot or piston. This launcher can be any conventional type wherefrom a projectile or piston is accelerated to a velocity of at least feet per second. The casing 1 may be attached to the muzzle 6 of the launcher tube by conventional means such as set screws 14 or directly screwed thereon as shown in FIG. 2. The bore of the muzzle, however, must not be greater than the entrance diameter of the bore 2 in the casing. At the front end of the casing is shown a tubular booster material 4 which is force-fitted into the bore 2. This booster material may be composed of a solid hydrogenous material, such as polyethylene, polypropylene, nylon, Teflon, Kel-F, wax, paraffin, lithium hydride, or a low atomic weight element such as solid hydrogen, lithium or beryllium. A sabot 3 is provided with a detachably mounted projectile 5 on its forward face. The sabot depicted in FIG. 1 is a solid cylindrical mass preferably of dense material, such as steel, tungsten or uranium, athough lower density metals, ceramics or plastics may also be used. The sabot 3 has a diameter equal to or slightly smaller than the bore diameter of the casing 1. The projectile 5 may be of any configuration such that its maximum diametral dimension transverse to its longitudinal axis is less than the minimum inside diameter of the booster tube or of the booster fluid at the instant of sabot impact. The projectile may be spherical as shown in FIG. 1 and is secured to the center of the forward face of the sabot or on a small forward protrusion of the sabot by a suitable wax, adhesive or plastic 13.

In operation the sabot with its attached projectile is fired by a conventional gun or other launcher so that the sabot enters the bore 2 of the casing 1. The sabot impacts the booster material, but the projectile 5 enters the booster material without touching it. As the sabot impacts the booster material, a shock wave is generated in the booster material which converts the material to a high pressure, high temperature fluid. The shock pressure in the booster material must exceed the yield strength of the booster material. The shocked booster fluid, then, is constrained by the outer casing 1 to move radially inward where it converges on the center line behind the projectile, and a portion of the fluid turns and escapes in a forward direction, forming a high velocity jet which impinges on the rear face of the projectile and accelerates the projectile relative to the sabot 3. As the shock wave proceeds axially through the booster material, shocked material is continually fed as a fluid radially inward into the region behind the projectile 5 providing a continuing fast jet and a continuous acceleration force on the projectile for a distance of several centimeters. Since the projectile mass is small compared to the mass of shocked booster in the fast jet, the projectile 5 is accelerated substantially. If the booster material is of a much lower density than the sabot material, the shock wave produced within the booster material causes an acceleration of the shock booster fluid to give it an axial velocity component almost equal to the initial velocity of the sabot 3 and projectile 5. Therefore, as the shocked material expands radially inward, it is initially moving with nearly the same axial velocity as the projectile 5, and the high pressure produced by the fast jet impinging on the rear side of the projectile can continuously accelerate the projectile to a higher velocity. This would not be true if the sabot and booster were of the same material or same density, in which case the axial velocity of the shocked material would be only approximately one-half of the initial sabot velocity, in which case the fast jet velocity would be lower and the velocity augmentation would be less effective. As the shocked booster fluid converges on the center line of the bore 2, it forms approximately a conical zone of converging fluid which acts very much like a Monroe shaped charge in accelerating solid or liquid particles along its axis. In a further embodiment, therefore, the invention can also utilize a solid explosive material as a booster, in which case an explosive detonation wave is produced in the booster by the sabot impact. Still further, the booster unit may consist of solid hydrogen or other solidified gas which is either inserted in the casing bore 2 immediately prior to firing, or is maintained in a solid state by external refrigeration. The booster material could be in a liquid form as well, although special precautions would be necesary as will be discussed hereinafter; for example,

liquid hydrogen, liquid helium, water or any other liquid may be used.

In one respect, non-explosive booster material is analogous to a solid or liquid shaped charge of explosive material wherein the role of the detonation wave in the shaped charge has been replaced by the shock wave generated in the booster material by sabot impact. At sufficiently high impact velocities of a sabot, the pressure, temperature and internal energy per unit volume attainable in a shocked booster of non-explosive material can actually exceed those values produced by detonation of a condensed phase explosive. Therefore, without using explosive materials the performance of explosive shaped charges with or without liners can be duplicated or surpassed in the production of high velocity gaseous jets, drag acceleration or projectiles by gaseous jets, or production of jets from a solid liner material. A detailed discussion of the aforementioned principle will be found in The Shock Plasma Acceleration Technique for Veocity Augmentation, by Wiliam C. Cooley, Proceedings of the Seventh Hypervelocity Impact Symposium, vol. 1, Techniques, February 1965, pages l02l23.

FIG. 2 depicts a form of the invention which utilizes a converging-diverging nozzle as part of the casing bore 2 to convert a large fraction of the thermal energy in the shock-produced gas into directed kinetic energy by expanding the gas to supersonic velocities in order to accelerate the projectile by drag force to a higher final velocity. The booster material is a liquid and a thin walled container 7a is provided to confine the liquid as shown in FIG. 2.

FIG. 3 depicts a diverging nozzle 8 at the exit end of the booster unit which functions in substantially the same manner as the nozzle 7 in FIG. 2, although the tapered section of the booster unit is consumed by the shock wave at the later stages of the acceleration process.

FIG. 4 illustrates the invention employing multiple stages for achieving increased velocities of the projectile. FIG. 4 depicts a two-stage embodiment of the invention for purposes of clarity. However, any number of stages can be utilized depending upon what the physical limitations of the system will allow. As in FIG. 1, there is shown in FIG. 4 the combination of elements, namely, the casing 1, with a bore 2, a sabot 3, a booster tube 4 and a projectile 5. In addition to these elements, however, there is a second sabot 3a and a second booster unit 40. The sabot 3a is detachably mounted, as by a wax, adhesive or plastic 13, to the center of the forward face of the first sabot 3. Attached to the second sabot, in the same manner as the two sabots are attached to each other, is the projectile 5. The second booster 4a is force-fitted into the casing bore 2 in the same manner as the first booster is fitted into said bore. The two boosters are adjacent each other with the second booster 4a located at the exit end of the casing. The inside diameter of the booster 4a must be smaller than both the inside diameter of booster 4 and the diameter of sabot 3a, but greater than any diametral dimension of projectile 5 transverse to its longitudinal axis. Additional stages consisting of smaller sabots and boosters cou'd be utilized. In principle, therefore, the multi-stage system can accelerate successively smaller stages to successively higher velocities.

FIG. 5 illustrates a further form of the invention wherein 1b is a casing having a cylindrical bore 2b which tapers to an increasing diameter at the exit or open end of the casing to form a diverging nozzle. At the point where the bore 2b assumes a constant diameter and extending rearwardly therefrom there is provided a booster tube 4b. This tube has a constant outside diameter over a portion of its length wherein its outside surface forms a force fit contact with the bore surface of the casing 1b. The booster tube 4b has a variable inside diameter decreasing rearwardly and a continuously variable wall thickness. A hollow cylindrical sabot 512 formed of the same material as sabot 3 is provided with a detachably mounted projectile 6b at the center of its forward face.

The projectile is shown as a sphere which is embedded in a small cavity 15 on the forward face of said sabot 5b to a depth of less than one sphere radius. The projectile sphere 6b is initially cemented into the cavity 15 with a conventional adhesive having a lower tensile strength than that of the sabot or projectile material. This structure allows the fluid produced by initial impact of the sabot 5b with the booster unit 4b to act on a portion of the rear portion of the projectile 6b in order to separate it from the sabot 5b and permit continued acceleration.

The sabot structure 5b is a modification of the sabot 3 in FIG. 1 in that it contains a depression 717 in its rear side in order that most of the sabot mass may be in a cylindrical section at the forward face to act as a high inertia platform from which the projectile 6b is launched. The design permits the length to diameter ratio of the sabot to remain near unity for greater stability in the gun barrel 6 and, further, to use a dense metallic sabot material and yet keep the sabot mass low enough that the sabot impact velocity is still high.

The variable inside diameter booster unit 4b, in FIG. 5, is seen to have its smallest internal diameter at the face where impact by the sabot takes place. However, this is not a necessary condition and the minimum internal diameter may occur at a point spaced away from the plane of impact. Of course, the minimum diameter must be greater than any given diameter of the projectile transverse to its longitudinal axis. This provision of an inside diameter and wall thickness which may vary along the axial direction of the booster unit 4b allows for controTling the time variation of pressure application to the projectile 6b in order to maximize the velocity increase and yet avoid excessive ablation or fracture of the projectile 6b.

The form of the invention shown in FIG. 6 utilizes a selfcontained explosive charge 6c located adjacent an end wall 70 in the casing 1c for luanching the sabot or driver plate and projectile 3c, Sc, along the center line of the bore 2c. A conventional electrical detonating means 12 is connected to the explosive charge through an opening 14 in the end wall 7c. When the charge 6c is exploded by the detonating means 12, the cylindrical sabot or driver plate 30 is propelled forward till it impacts the booster unit 4c whereupon the projectile 5c is accelerated forward to a hypervelocity in the same manner as previously described.

FIGS. 7l0 illustrate another form of the invention wherein a liquid booster material 24 is utilized within the casing 20 which is formed with a nozzle exit 33. Referring to FIG. 7, the casing 20 is seen to have an end wall next to which is located an explosive charge 22. A sabot in the form of a cylindrical piston member 21 is positioned in front of said charge. The sabot may or may not be mounted with a projectile 23. Near the forward end of the casing there is provided a passageway 25 leading from a check valve 26 on the outside of said casing to an outlet port 25a on the inside surface of the bore of said casing, the axis of said passageway being tangential to the bore surface of the casing, see FIG. 8. A liquid booster material is housed in a supply container 28 under gas pressure means 30. This pressure is controlled by regulator 29. By means of the control valve 27 the liquid booster material may be fed to said passageway 25 through the tubing 32. A check valve of conventional construction connects said tubing to said passageway. The object, therefore, is to feed a given amount of booster material under pressure to said passageway 25, whereupon the booster liquid will leave the tangentially oriented outlet port 25a and spin around the curved surface of the bore. At this point the explosive charge can be detonated to fire the sabot 21 toward the swirling liquid booster material, see FIGS. 9 and 10. To accomplish the above operations by merely using a Single initiating means, a conventional electrical timing means 31 is connected between the detonating means 34 and the control valve 27. The timing means is set to operate the control valve 27 just prior to initiating the detonating means 34. The timing means may be operated by a simple plunger switch 35.

Impact with the liquid booster material by the sabot 21 will cause a shock wave to be generated in the manner previously described. The sabot may be used without a projectile, in which case a pulsed fluid jet of high stagnation pressure and temperature is accelerated through the nozzle 33. Such pulsed jets could be used in shock tunnels for aerodynamic research.

More than one passageway may be provided to feed the liquid 'booster to the casing bore. For example, a plurality of radially extending passageways could terminate into tangentially oriented ports on the surface of the casing bore. Further, the illustration in FIG. 8 shows a single operation device. However, an automatic device could be developed by providing means for replacing the charge automatically after each explosion. A permanent sabot or piston could be utilized with an automatic operation otherwise the ordinary destructible sabot would similarly have to be replaced with each charge.

Successful experiments have been conducted utilizing the principles of this invention, which experiments have been recorded and may be found in the following publications: The Theory of Shock Hydrodynamic Velocity Augmenters, by W. C. Cooley and A. E. Seigel for the National Aeronautics and Space Administration, Langley Research Center, Hampton, Va., Mar. 1, 1965, and A Research Study of a Velocity Augmentation System and Development of a Prototype Infrared Penetration Detector, The National Aeronautics and Space Administration, Langley Research Center, Hampton, Va., Mar. 1, 1965.

That which is claimed is:

1. In a hypervelocity projectile launcher the combination of a cylindrical casing having an axial bore, a cylindrical sabot coaxially aligned with said bore, means for detachably mounting a projectile at the center of one end face of said sabot, a sleeve of non-explosive material having a lower density than said sabot longitudinally extending along a portion of said bore, the inside diameter at any given location of said sleeve being less than the diameter of said cylindrical sabot but substantially greater than any given diametral dimension of said projectile transverse to its longitudinal axis, and means for propelling said sabot along the axis of said bore to strike said sleeve for generating a shock Wave therein whereby said qsjleeve is converted into a fluid jet along the axis of said ore.

2. A device according to claim 1, wherein said casing is provided with an end wall and the means for propelling said sabot is an explosive charge located adjacent said wall and being provided with electrical detonating means extending through an opening in said wall.

3. In a hypervelocity jet device the combination of a cylindrical casing having an axial bore, a cylindrical sabot coaxially aligned with said bore, a sleeve of nonexplosive material having a lower density than the density of said cylindrical sabot longitudinally extending along a portion of said bore and defining a coaxial space within said bore, the inside diameter at any given location of said sleeve being less than the diameter of said sabot, and means for propelling said sabot along the axis of said bore to strike said sleeve for generating a shock wave therein whereby said sleeve is converted into a fluid jet along the axis of said bore.

4. The device according to claim 3, wherein aid nonexplosive material incorporates low atomic weight elements.

5. The device according to claim 3, wherein said nonexplosive material is a fluid which is confined by a thin walled solid container extending on the inside surface of said bore.

6. The device according to claim 3, wherein a portion of said bore adjacent said sleeve has a variable inside diameter to form a nozzle.

7. In a system for producing a hypervelocity fluid jet, the combination of a cylindrical casing having an axial bore with an end face and an open exit end, a cylindrical piston member positioned within said bore and spaced from said exit end, means positioned adjacent said end face for driving said piston towards said exit end, said casing having a transversely extending passage and outlet port tangentially disposed to the surface of said bore between said piston member and said exit end, means for supplying a non-explosive fluid booster material under pressure to said passage, timing means connecting said supply means and said driving means, initiating means for operating said timing means to operate said supply means for providing a given quantity of fluid booster material to said passage in timed relation to the initiation of said driving means, whereby said piston is caused to impact with said given quantity of booster material for generating a shock Wave therein and convert said booster material into a fluid jet along the axis of said bore.

8. A device according to claim 7, wherein means is provided for detachably mounting a projectile to the forward face of said piston whereby the hypervelocity jet caused 'by said impact accelerates said projectile past the exit end of said casing.

9. In a system for producing a hypervelocity fluid jet, the combination of a cylindrical casing having an axial bore with an end face and an open exit end, a piston member positioned Within said bore and spaced from said exit end, said casing having a transversely extending passage and outlet port tangentially disposed to the surface of said bore between said piston member and said exit end, means supplying a non-explosive fluid booster material to said passage for positioning a given quantity of said booster material circumferentially along the surface of a section of said bore, and means positioned adjacent said end face for driving said piston toward said exit end, whereby said piston is caused to impact with said given quantity of booster material for generating a shock wave therein and convert said booster material into a fluid jet along the axis of said bore.

10. In a system for producing a hypervelocity fluid jet for impacting and disintegrating materials, the combination of a casing having an axial bore with an end face and an open exit end, a piston member having an impact surface positioned within said bore and spaced from said exit end, said casing having an inlet port disposed substantially normal to the axis of said bore between said piston member and said exit end, means supplying a non-explosive fluid booster material through said inlet port to said bore for positioning a given mass of said booster material at the forward end of said bore, means positioned adjacent said end face for driving said piston member toward said exit end, and timing means for controlling the injection of said booster material and the means for driving said piston, whereby said piston member is caused to impact with said given mass of booster material for generating a shock wave therein and converting said booster material into a fluid jet along the axis of said bore.

11. In a system for producing a hypervelocity fluid jet for impacting and disintegrating materials, the combination of a casing having an axial bore with an end face and an open exit end, a piston member having an impact surface positioned within said bore and spaced from said exit end, supply means mounted on said casing spaced from said piston supplying a non-explosive fluid booster material to said bore for positioning a given mass of said booster material in said bore, means positioned adjacent said end face for driving said piston member toward said exit end, and timing means for controlling the injection of said booster material and the means for driving said piston, whereby said piston member is caused to impact with said given mass of booster material for generating a shock wave therein and converting said booster material into a fluid jet along the axis of said bore.

12. In the system according to claim 11 wherein said open exit end of said bore is provided with a nozzle having a diameter substantially smaller than the diameter of said bore of said casing.

References Cited UNITED STATES PATENTS 57,607 8/1866 White 89-8 2,435,647 2/1948 Engseth 103153 2,837,971 6/1958 Wesak 89-5 3,249,046 5/1966 Balchan et al. 10222 SAMUEL W. ENGLE, Primary Examiner US. Cl. X.R. 102-22 

